U.S. patent application number 10/647887 was filed with the patent office on 2004-05-13 for process for the preparation of doped pentasil-type zeolites using doped faujasite seeds.
Invention is credited to Rao, Rajeev S..
Application Number | 20040091420 10/647887 |
Document ID | / |
Family ID | 39428121 |
Filed Date | 2004-05-13 |
United States Patent
Application |
20040091420 |
Kind Code |
A1 |
Rao, Rajeev S. |
May 13, 2004 |
Process for the preparation of doped pentasil-type zeolites using
doped faujasite seeds
Abstract
Process for the preparation of doped pentasil-type zeolite,
which process comprises the steps of: a) preparing an aqueous
precursor mixture comprising a silicon source, an aluminum source,
doped faujasite seeds, and another type of seeding material, and b)
thermally treating the precursor mixture to form a doped
pentasil-type zeolite. This process results in doped pentasil-type
zeolites in a shorter crystallization time compared to prior art
processes.
Inventors: |
Rao, Rajeev S.; (Webster,
TX) |
Correspondence
Address: |
LOUIS A. MORRIS
AKZO NOBEL INC.
7 LIVINGSTONE AVENUE
DOBBS FERRY
NY
10522-3408
US
|
Family ID: |
39428121 |
Appl. No.: |
10/647887 |
Filed: |
August 25, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60406491 |
Aug 28, 2002 |
|
|
|
Current U.S.
Class: |
423/709 ;
423/713 |
Current CPC
Class: |
Y10S 423/29 20130101;
Y10S 423/22 20130101; Y10S 423/34 20130101; C01B 39/36
20130101 |
Class at
Publication: |
423/709 ;
423/713 |
International
Class: |
C01B 039/06 |
Claims
1. a Process for the preparation of doped pentasil-type zeolite
comprising the steps of: a) preparing an aqueous precursor mixture
comprising a silicon source, an aluminum source, doped faujasite
seeds, and another type of seeding material, and b) thermally
treating the precursor mixture to form a doped pentasil-type
zeolite.
2. The process of claim 1 wherein the doped pentasil-type zeolite
is doped ZSM-5.
3. The process of claim 1 wherein the other type of seeding
material comprises pentasil-type seeds.
4. The process of claim 1 wherein the other type of seeding
material is a sol or gel containing an organic directing
template.
5. The process of claim 1 wherein the faujasite seeds are doped
with a dopant selected from the group consisting of Ce, La, Mn, Fe,
Ti, Zr, Cu, Ni, Zn, Mo, W, V, Sn, Pt, Pd, Ga, B, and P.
6. The process of claim 1 wherein the silicon source is selected
from the group consisting of sodium silicate, sodium meta-silicate,
stabilized silica sols, silica gels, polysilicic acid, tetra
ethylortho silicate, fumed silicas, precipitated silicas, and
mixtures thereof.
7. The process of claim 1 wherein the aluminum source is selected
from the group consisting of Al.sub.2(SO.sub.4).sub.3, AlCl.sub.3,
AlPO.sub.4, Al.sub.2(HPO.sub.4).sub.3, Al(H.sub.2PO.sub.4).sub.3,
aluminum trihydrate (Al(OH).sub.3), thermally treated aluminum
trihydrate, (pseudo)boehmite, aluminum chlorohydrol, aluminum
nitrohydrol, and mixtures thereof.
8. The process of claim 1 wherein step b) is performed at a
temperature in the range 150-180.degree. C.
9. The process of claim 1 wherein step b) is performed for 3-8
hours.
10. The process of claim 1 wherein a shaping step is performed
between steps a) and b).
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Application
Serial No. 60/406,491, filed Aug. 28, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the preparation of doped
pentasil-type zeolites using doped faujasite seeds.
[0004] 2. Prior Art
[0005] U.S. Pat. No. 5,232,675 discloses a process for the
preparation of rare earth metal (RE)-doped pentasil-type zeolites
using RE-doped faujasite seeds. The process involves the steps of
dispersing the RE-doped faujasite seeds in a gel system comprising
water glass, aluminum salt, inorganic acid, and water, and
crystallising the resulting mixture at a temparture of
30-200.degree. C. for 12-60 hours.
[0006] The present invention provides a process for the preparation
of rare earth metal-doped pentasil-type zeolites which requires a
shorter crystallization time than the prior art process.
SUMMARY OF THE INVENTION
[0007] In one embodiment, the process of the invention comprises
the steps of:
[0008] a) preparing an aqueous precursor mixture comprising a
silicon source, an aluminum source, doped faujasite seeds, and
another type of seeding material, and
[0009] b) thermally treating the precursor mixture to form a doped
pentasil-type zeolite.
[0010] Other embodiments of the invention encompass details
concerning precursor mixture compositions and process steps, all of
which will be hereinafter discussed in detail.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The process of the invention requires the use of doped
faujasite seeds. Examples of faujasite seeds are zeolite X and
(ultrastabilized) zeolite Y.
[0012] The term "doped faujasite seeds" refers to faujasite seeds
containing an additive (also called dopant). Suitable dopants
include compounds comprising rare earth metals such as Ce or La,
alkaline earth metals such as Mg, Ca, and Ba, transition metals
such as Zr, Mn, Fe, Ti, Cu, Ni, Zn, Mo, W, V, and Sn, actinides,
noble metals such as Pt and Pd, gallium, boron, and/or phosphorus.
Suitable compounds are the oxides, hydroxides, carbonates,
hydroxycarbonates, chlorides, nitrates, sulfates, and phosphates of
the above elements.
[0013] The dopant is present in the faujasite seed in amounts of
1-50 wt %, preferably 1-25 wt %, more preferably 5-20 wt %, and
most preferably 10-20 wt %, calculated as oxide and based on the
dry weight of the doped faujasite seeds.
[0014] Doped faujasite seeds can be prepared by, e.g.,
ion-exchange, impregnation, and solid state exchange of the
faujasite seeds with the dopant. These procedures are well-known to
the skilled person.
[0015] Furthermore, at least one other type of seeding material is
used in the process. The term "other type of seeding material"
refers to templates or seeds other than doped faujasite seeds.
Suitable other types of seeding materials include pentasil-type
seeds (e.g. ZSM-5 seeds, ZSM-11 seeds, zeolite beta seeds, etc.),
any other type of seed or template generally applied in ZSM-5
synthesis, such as sols or gels containing an organic directing
template such as tetrapropyl ammonium hydroxide (TPAOH) or
tetrapropyl ammonium bromide (TPABr). An example of such a
template-containing sol is a Si-Al sol containing 0.1-10 wt % of
tetrapropyl ammonium bromide.
[0016] If desired, the other type of seeding material is doped.
Suitable dopants include compounds comprising rare earth metals
such as Ce and La, alkaline earth metals such as Mg, Ca, and Ba,
transition metals such as Mn, Fe, Ti, Zr, Cu, Ni, Zn, Mo, W, V, and
Sn, actinides, noble metals such as Pt and Pd, gallium, boron,
and/or phosphorus.
[0017] The optional dopant(s) present in the other type of seeding
material can be the same as or different from the dopant(s) present
in the doped faujasite seeds.
[0018] The pentasil-type zeolite resulting from the process
according to the invention preferably has a
SiO.sub.2/Al.sub.2O.sub.3 ratio (SAR) of 25-90. Typical examples of
pentasil-type zeolites are ZSM-type zeolites, such as ZSM-5,
ZSM-11, ZSM-12, ZSM-22, ZSM-23, and ZSM-35, zeolite beta, and
zeolite boron beta. The doped pentasil-type zeolite preferably
contains 0.1-10 wt %, more preferably 0.1-3 wt %, and most
preferably 0.5-2.5 wt % of dopant, calculated as oxide and based on
the total dry weight of the doped zeolite.
[0019] The first step of the process according to the invention
involves the preparation of an aqueous precursor mixture comprising
a silicon source, an aluminum source, doped faujasite seeds, and at
least one other type of seeding material.
[0020] Suitable aluminum sources include aluminum salts, such as
Al.sub.2(SO.sub.4).sub.3, AlCl.sub.3, AlPO.sub.4,
Al.sub.2(HPO.sub.4).sub- .3, and Al(H.sub.2PO.sub.4).sub.3, and
water-insoluble aluminum compounds, e.g., aluminum trihydrate
(Al(OH).sub.3) such as gibbsite and bauxite ore concentrate (BOC),
thermally treated aluminum trihydrate such as flash-calcined
aluminum trihydrate, (pseudo)boehmite, aluminum chlorohydrol,
aluminum nitrohydrol. Also mixtures of one or more of these
aluminum sources can be used.
[0021] Alternatively, doped aluminum sources can be used. Examples
of such doped aluminum sources are doped (pseudo)boehmite and doped
aluminum trihydrate.
[0022] Doped aluminum sources can be obtained by preparing the
aluminum source in the presence of a dopant, impregnating the
aluminum source with a dopant, or ion-exchanging the aluminum
source with a dopant.
[0023] Doped (pseudo)boehmite for instance can be prepared by
hydrolysis of aluminum alkoxide in the presence of a dopant,
hydrolysis and precipitation of aluminum salts in the presence of a
dopant, or by aging a slurry of (thermally treated) aluminum
trihydrate, amorphous gel alumina, or less crystalline
(pseudo)boehmite in the presence of a dopant. For more information
concerning the preparation of doped (pseudo)boehmite reference is
made to International Patent Application Nos. WO 01/12551, WO
01/12552, and WO 01/12554.
[0024] Suitable silicon sources include sodium silicate, sodium
meta-silicate, stabilized silica sols, silica gels, polysilicic
acid, tetra ethylortho silicate, fumed silicas, precipitated
silicas, and mixtures thereof. Also doped silicon sources can be
used. Doped silicon sources can be obtained by preparing the
silicon source in the presence of a dopant, impregnating the
silicon source with a dopant, or ion-exchanging the silicon source
with a dopant.
[0025] Doped silica sol for instance can be prepared by preparing a
silica sol from water glass and acid (e.g. sulfuric acid) and
exchanging the sodium ions with the desired dopant. Alternatively,
water glass, acid (e.g. sulfuric acid), and dopant are
coprecipitated to form a doped silica sol.
[0026] Suitable dopants for the aluminum and/or the silicon source
include compounds comprising rare earth metals such as Ce and La,
alkaline earth metals such as Mg, Ca, and Ba, transition metals
such as Mn, Fe, Ti, Zr, Cu, Ni, Zn, Mo, W, V, and Sn, actinides,
noble metals such as Pt and Pd, gallium, boron, and/or
phosphorus.
[0027] The optional dopant(s) present in the silicon and/or the
aluminum source and the dopant in the doped faujasite seeds can be
the same or different.
[0028] The precursor mixture preferably contains 0.1-10 wt %, more
preferably 0.510 wt % of doped faujasite seeds and preferably 1-10
wt %, more preferably 1-5 wt % of the other type of seeding
material, based on dry weight of the precursor mixture.
[0029] The amounts of silicon and aluminum source present in the
precursor mixture depend on the desired SAR of the resulting doped
pentasil-type zeolite.
[0030] If so desired, several other compounds may be added to the
precursor mixture, such as metal (hydr)oxides, sols, gels, pore
regulating agents (sugars, surfactants), clays, metal salts, acids,
bases, etc.
[0031] Furthermore, it is possible to mill the precursor
mixture.
[0032] The second step of the process involves thermal treatment of
the precursor mixture at temperatures ranging from 130 to
200.degree. C., preferably 150-180.degree. C., for 3-60 hrs,
preferably 1-11 hrs, and most preferably 3-8 hrs. During this step,
the doped pentasil-type zeolite is formed by crystallization.
[0033] The thermal treatment can be conducted in one or more
reaction vessels. If more than one such vessel is used, the process
is preferably conducted in a continuous mode. Using more than one
reaction vessel further makes it possible to prepare the aqueous
precursor mixture either by adding all ingredients to the first
vessel, or by dividing the addition of (part of the total amount
of) the ingredients over the reaction vessels.
[0034] The precursor mixture of step a) or the doped pentasil-type
zeolite resulting from step b) can be shaped to form shaped bodies.
Suitable shaping methods include spray-drying, pelletising,
extrusion (optionally combined with kneading), beading, or any
other conventional shaping method used in the catalyst and
absorbent fields or combinations thereof.
[0035] When shaping the precursor mixture of step a), the amount of
liquid present in the precursor mixture should be adapted to the
specific shaping step to be conducted. It may be advisable to
partially remove the liquid used in the precursor mixture and/or to
add an additional or another liquid, and/or to change the pH of the
precursor mixture to make the mixture gellable and thus suitable
for shaping. Additives commonly used in the different shaping
methods, e.g., extrusion additives, may be added to the precursor
mixture used for shaping.
[0036] If so desired, the resulting doped pentasil-type zeolite may
be calcined and optionally ion-exchanged.
[0037] The doped pentasil-type zeolite can be used in or as a
catalyst composition or catalyst additive composition for, e.g.
hydrogenation, dehydrogenation, catalytic cracking (FCC), and
alkylation reactions.
EXAMPLES
Comparative Example 1
[0038] A precursor mixture was prepared by combining 2,007 g water
glass, 208 g aluminum sulfate, 141 g of 98% H.sub.2SO.sub.4, 2,466
g water, and 45 g Y-zeolite seeds doped with 12 wt % RE (calculated
as oxide).
[0039] The precursor mixture was treated at 170.degree. C. at
autogeneous pressure for 12 hours. The characteristics of the
resulting pentasil-type zeolite are presented in Table 1 below.
[0040] This Example shows that Y zeolite as such can act as a seed
for the nucleation of pentasil-type zeolites.
Comparative Example 2
[0041] Comparative Example 1 was repeated, except that the
precursor mixture was treated at 170.degree. C. for 6 hrs. The
results are shown in Table 1 below.
[0042] This Example indicates that under these reaction conditions
a crystallization time of 6 hrs is inadequate for the formation of
significant amounts of pentasil-type zeolite.
Example 3
[0043] Comparative Example 2 was repeated, except that, in addition
to the other compounds, 6.5 g of ZSM-5 seeds were added to the
precursor mixture.
[0044] The characteristics of the resulting pentasil-type zeolite
are also presented in Table 1. This Example clearly shows that the
addition of another type of seed accelerates the crystallization.
So, in the presence of this seed, a crystallization time of 6 hrs
is adequate.
1 TABLE 1 Comp. Example 1 Comp. Example 2 Example 3 BET-surface 316
37 320 area (m.sup.2/g) Micropore 0.1227 0.0116 0.1193 volume
(ml/g) % ZSM-5.sup.1 85 6 83 .sup.1The % ZSM-5 refers to the
relative crystallinity of the sample, which was determined by X-ray
diffraction using copper K-alpha radiation. The sample's total net
integrated intensity of the reflections within the 2.theta.-range
of 20-25.degree. was determined and compared with that of a
monoclinic ZSM-5.
* * * * *